1. Field of the Invention
The present invention relates to a method of recycling and granulating waste container made of thermoplastic resin materials.
In more detail, this invention relates to treating waste containers made of thermoplastic resin materials (hereinafter also called "resinous containers"), which are used in an enormous number edible oils such as tem-pura (deep-fried fish and vegetables) oil, sesame oil, and salad oil; for viscous fluids such as Worcester sauce, mirin (sweet sake as seasoning) and dressings (hereinafter called "containers for viscous fluids"); for various types products such as beverages, shampoo, detergents, eye lotion, vinegar, soy sauce, sake, and beer; wherein metal parts are removed from the waste resinous containers; the resin part is shredded in a broader sense crushed into small pieces; foreign objects including residual contents such as oils, viscous fluids, beverages and other products for daily use as well as foreign matters such as rain water, dew, mud, soil, sand, and dirt clung adhering small pieces to the coarsely crushed pieces are separated and removed; each type of reusable resin materials is separated, recycled and granulated; thus, this invention relates to a method for recycling and granulating reusable resin materials. Also, the recycled granules are further granulated into more uniform grain sizes, which are directly molded into products such as fibers and other forms of products, or into pellets; thus, the present invention relates to the method for implementing all of these processes.
Resinous containers mentioned above include bottles made of resin materials such as polyester (polyethylene terephthalate or PET, hereinafter called "PET bottles"), polyethylene (hereinafter called "PE bottles"), and poly(vinyl chloride) or PVC (hereinafter called "PVC bottles").
2. Description of the Prior Art
The resinous containers mentioned above (hereinafter simply called "containers") such as PET bottles are used to contain oily products, viscous fluids, beverages, and other types of products for daily use. Recent development of stretch-blowing technique made it possible to produce less expensive and high-performance PET bottles, which has resulted in an enormous number of discarded waste containers. The total weight of waste PET bottles is said to be 10,000 tons per month in Japan; consequently, recycling of waste PET bottles has become a social demand.
Such waste stretch-blown containers (hereinafter simply called "waste containers") made of poly(vinyl chloride) (PVC), polyester (PET), and polyethylene (PE) are discarded after consumption of the contained products, the discarded bottles are contaminated with foreign matters such as mud, soil, sand, and dirt. Conventionally, these containers have been collected, washed with water to remove the foreign objects, dried, crushed, and recycled into fibers or blow-molded piles for the replacement of wood.
These containers are resistant to water, weather, and corrosion; also PVC, in particular, generates a large amount of harmful gas and smoke when incinerated to disrupt the environment. Further, the melted resin materials stick to the furnace wall to spoil the furnace. To solve these problems, those waste containers are being used for a landfill, wherein the waste resin remains uncorroded over an extended period, they appear to present another factor for environmental disruption.
On the other hand, such resin materials will yearly be exhausted due to resource depletion, and it is now demanded and recognized that the post-reuse resin materials must be recycled without disposal.
Conventionally, the waste containers have been washed with water for removal of the foreign objects and processed for recycling. The process includes washing and drying, requiring a large amount of water and a large equipment.
In particular, oily materials such as tem-pura oil, sesame oil, and salad oil are harder to separate from the waste container, compared with other materials; e.g., washing with water could hardly remove these foreign objects and special detergents had to be used. Washing harmful materials such as surfactants with water contaminated rivers and had to be neutralized before draining, adding additional high costs of facility and operation.
Viscous fluids such as Worcester sauce, dressing, and mirin are easier to separate than the ones above mentioned oily materials, while the viscosity sometimes has caused troubles in washing off these materials by water.
Other products such as beverages, shampoo, detergents, eye lotion, vinegar, soy sauce, sake, and beer than the above mentioned oily or viscosity ones may be purified by water, while some of these products contain harmful ingredients such as a detergent which must be neutralized before draining and added high costs to facility and operation. Most of the waste containers have been discarded without recycled, because of these problems caused by the difficulties in washing, added high costs in facility and operation, and waste of a large amount of water and energy resources.
The present invention is to solve these problems providing a method for separating and removing foreign objects such as the residual content, mud, soil, sand, and dirt from the containers to be treated, efficiently recycling and granulating the resin materials into a specific range of size, in a relatively simple manner.